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BQ25895: BQ25895 Charger issues

Shlomi Yehezkia
Mastermind 6150 points
Part Number: BQ25895

Hi TI Team, 

Could you please review and assist with the charger schematic (Page 10, U6).

The charger doesn't work. It doesn't charge the battery. 

Please find the schematic attached.

Thanks,

Shlomi

es3_b0_2018_03_03.pdf

  • 0
    TI__Guru 57541 points

    Could you please provide all register values when the device does not charge? Thanks!

  • 0 in reply to Ning T
    Guru 13485 points

    See below customer feedback:

    The problem is not in battery charging, but in system startup.

    When “normal” battery is connected, (by “normal” I mean not completely discharged battery), system draws some current from battery, starts up well and battery charge cycle completes as intended. When the battery is not connected, the charger enters some strange 180-200mA current limit mode (I assume that this is so called “soft start” limit, mentioned in one place in the datasheet), which is clearly not enough for buck-boost and following SOM to start up.

    The registers setting is as it should be after power-up, without any modification. The current limiting resistor I changed to 0, and shorted D=/D-, so I expect the input current limit to correspond to USB DCP, i.e. 3.2A. This current limit is actually applied after ~2s after the power is up. If I manually delay by few seconds buck-boost start up than the system could start, as this initially was intended to be done by microcontroller.

    I can ask TI only one thing: is it possible to remove this “soft start” current limit or increase it? And if the answer is “no”, then we will have to replace to hell this damned charger.

  • 0 in reply to eli
    TI__Guru 57541 points
    When battery is not connected and charge is enabled, the device tries to regulate VBAT to battery charge limit (e.g. 4.208V), then terminate, after certain time VBAT may drop below recharge threshold, device will charge VBAT to charge voltage again, so the charger status switches between charging and charging complete and STAT pin blinks. You can prevent this by disabling charge when the battery is removed. Please try and see if this helps.
    Thanks!